Splatter vs Clean Signal at High Wattage

[sunwave]

I do not want to be all phd level in this. Really is to question why some or most om CB choose to splatter when it is possible to have a strong signal without splatter. Really is no excuse anymore given current technology can eliminate that.

In my elementary level image all I care to show splatter vs clean signal. Voice of America 17.655Mhz is kicking out 100 times more wattage than most on channel 6 is and it's clean as a shiny new ring. Amateur radio Linears at 1.5kw are almost or just as clean. Both are amplitude modulated (A.M.)



Why are cb'ers preferring the dirty signal?

 

[prcguy]

Many possible reasons and different stations will have different problems or multiple problems going on at the same time. One is the use of a class C RF amplifier which is not linear and produces distortion. For faithful amplification of AM or SSB signals a linear amplifier is needed like class AB, etc. Another problem is gross amplifier overdrive. An AM signal increases peak power by up to 6dB or 4X the carrier level under full modulation. That means if you have an actual linear 100w amplifier the most carrier level you can run on the output is about 25 watts so the amplifier can do its 100 watts at full modulation.

How many people do you know with a 100w amplifier that demand it puts out 100 watts at keydown, otherwise they think its broken? Doing this creates all kinds of distortions and with a 100w carrier the amplifier wants to put out about 400 watts during full modulation but it can't because the transistors are run into saturation at 100 watts and all it can do is spew out crap.

Then there are the people with the swing thing, using a non linear driver amplifier that is designed to increase gain when driven harder. This can take a properly operating radio that might put out 4w carrier and 12w peaks at full modulation and give you maybe a few watts of carrier and 70 to 100 watts during peak modulation. Then they drive a larger amplifier that saturates prematurely and distorts even more. Or if they are successful, the resulting AM signal that should have about 6dB of peak power during full modulation is now 10dB or more and it looks impressive on the meter at the receive end, but the AGC in the receiving radio can't handle the huge change in signal level during modulation.

 

[prcguy]

I forgot to mention a bad signal out of the radio due to amplified mics and cutting out the modulation limiter causing lots of splatter. Either of these can create flat top distortion in the RF envelope and the sharp edges of the distorted transmit audio can have harmonics way beyond the typical 3-4KHz upper limits of voice reproduction in the modulator circuits. When you see someone on a spectrum analyzer key up and take up massive bandwidth when they talk its often the transmit audio circuits creating the distorted and very wide audio signal that modulates the transmitter with 2X the bandwidth of the modulating signal. If someone has a 10KHz wide transmit audio signal the RF signal will be at least 20KHz wide and if its distorted then multiply the BW several times over.

Now stick that into a class C amplifier that is way overdriven and you have a real party brewing. When just one of these idiots key up its everyone out of the pool!

 

[slowmover]

CB choose to splatter when it is possible to have a strong signal without splatter

Choose is the debatable part of the statement.

Leaving aside those who intentionally screw up AM-19, and keeping things to base operators talking Skip on other channels, one sufficiently narrows the approach:

A). There’s those wishing to participate, but haven’t much of a budget.

B). There’s those could buy a new Chevrolet Colorado for what their station replacement cost would equal.

The latter really hasn’t an excuse.

The former are limited by gear quality and willful ignorance.

None of this applies to AM-6 where the Doors of Hell are kept ajar.

.

 

[slowmover]

Fight fahr wit’ fahr

OP, gitcha a Cobra 29 done up by T-Bone (Houston, TX), an Antron 99 maybe 20’ in air (tuned with $30 SWR meter), and a Texas Star TS350 from Copper.

Run a Red Devil power mic.

A “maybe” 30A (intermittent) power supply. Ground it to the plumbing.

Listen across a Cobra S100 speaker.

That’s the starting point for understanding.

You’re willing to go thru that station step-by-step (real thing, no hypothetical), it’d be a service to them and those that’d help them.

Get a few on-air friends involved. Before & After.

When the chips were down (COVID hoax) ARRL cancelled meets and pointedly ignored the most useful tool in the arsenal for men to continue to buy, sell, trade while avoiding close contact.

Your use of the words “choose” and “prefer” indicate a bias not worthy of respect. Your evident technical acumen holds a solution which — put to proper use — would be beneficial in the broadest sense (earned respect).

One can look long and hard to find a step-by-step model of ordinary base station gear (outlined above) taken to what you’ll define as respectable performance and he’ll not find it.

That’s the real answer to your question.

Alan Applegate took on the more difficult subject of Mobile Radio . . having asked himself similar questions.

.

 

[slowmover]

Mower Junkie is one step above what’s asked.
The man who already has something decent (safe) at work.